1. Field of Invention
The present invention relates to a process using radiofrequency microwave energy for the destruction of contaminated material consisting essentially of chemical and biological agents and harmful medical waste.
2. Background
In today""s modern world much contaminated waste is generated. Such contaminated waste may contain chemical and biological agents that are harmful to humans. In a conventional process for the destruction of these chemical and biological agents and harmful medical waste high temperatures are employed to incite incineration. In the field of chemistry this breaking up of molecules by heat is generally called pyrolysis, thus, such destruction is pyrolytic elimination. Since such products of pyrolysis may themselves be harmful, further treatment must be considered before release.
Conversely the subject process employs microwaves to destroy these chemical and biological agents and harmful medical waste. This process keeps the bulk temperature down to a modest level below about 300xc2x0 F. To further enhance the effect of microwaves at low temperatures, carbonaceous material is employed. The gaseous products of such microwave pyrolysis are further treated by additional microwaves that enhance their catalytic oxidation to environmentally releasable substances.
It is noted that chemical agents and biological agents are a special class of chemicals and are not identical to a hazardous material classification. Chemical agents are commonly related to xe2x80x9cpoisonous gaseousxe2x80x9d and other such chemical compounds and are often employed in warfare or terrorist activities. In World War I mustard gas, C4H8Cl2S, was so employed as was cyanide gases.
Biological agents although composed of organic molecules in a microorganism form have a special designation of being able to severely and usually fatally attack living organisms. Anthrax spores are such a biological agent and are employed in terrorist activities. Such biological agents are potentially carried by gas or liquid streams or may be clinging to material, such as cloth, metals, or other solids. In a liquid medium, such biological agents are often in a largely water arena; however, other biological cultures, which can be harmful or not, are often present. For instance, milk or its liquid food equivalents is such a biological culture and might be so contaminated; thus, in this instance the subject invention would substitute for a type of pasteurization process.
Potentially harmful waste occurs from medical processes, such as anything blood stained or contaminated with body solids or fluids. This medical waste is commonly solid material but its virgin pyrolyzed gaseous products have been recently recognized as potentially hazardous by a governmental agency. A common situation occurs in the Navy on board ships and submarines where space is limited and medical operations must proceed in a safe, but rapid manner.
Thus the subject invention deals with harmful agents and waste and not hazardous material, which is associated with various chemicals so identified by governmental regulations that cannot be routinely released into the environment, or if found in the environment, must be specially processed to avoid human contact and exposure.
Quantum radiofrequency (RF) physics is based upon the phenomenon of resonant interaction with matter of electromagnetic radiation in the microwave and RF regions since every atom or molecule can absorb, and thus radiate, electromagnetic waves of various wavelengths. The rotational and vibrational frequencies of the electrons represent the most important frequency range. The electromagnetic frequency spectrum is usually divided into ultrasonic, microwave, and optical regions. The microwave region is from 300 megahertz (MHz) to 300 gigahertz (GHz) and encompasses frequencies used for much communication equipment. For instance, refer to Cook, Microwave Principles and Systems, Prentice-Hall, 1986.
Often the term microwaves or microwave energy is applied to a broad range of radiofrequency energies particularly with respect to the common heating frequencies, 915 MHz and 2450 MHz. The former is often employed in industrial heating applications while the latter is the frequency of the common household microwave oven and therefore represents a good frequency to excite water molecules. In this writing the term xe2x80x9cmicrowavexe2x80x9d or xe2x80x9cmicrowavesxe2x80x9d is generally employed to represent xe2x80x9cradiofrequency energies selected from the range of about 500 to 5000 MHz,xe2x80x9d since in a practical sense this large range is employable for the subject invention.
The absorption of microwaves by the energy bands, particularly the vibrational energy levels, of atoms or molecules results in the thermal activation of the nonplasma material and the excitation of valence electrons. The nonplasma nature of these interactions is important for a separate and distinct form of heating employs plasma formed by arc conditions at a high temperature, often more than 3000xc2x0 F., and at much reduced pressures or vacuum conditions. For instance, refer to Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Edition, Supplementary Volume, pages 599-608, Plasma Technology. In microwave technology, as applied in the subject invention, neither of these conditions is present and therefore no plasmas are formed.
Microwaves lower the effective activation energy required for desirable chemical reactions since they can act locally on a microscopic scale by exciting electrons of a group of specific atoms in contrast to normal global heating which raises the bulk temperature. Further this microscopic interaction is favored by polar molecules whose electrons become easily locally excited leading to high chemical activity; however, nonpolar molecules adjacent to such polar molecules are also affected but at a reduced extent. An example is the heating of polar water molecules in a common household microwave oven where the container is of nonpolar material, that is, microwave-passing, and stays relatively cool.
In this sense microwaves are often referred to as a form of catalysis when applied to chemical reaction rates; thus, in this writing the term xe2x80x9cmicrowave catalysisxe2x80x9d refers to xe2x80x9cthe absorption of microwave energy by carbonaceous materials when a simultaneous chemical reaction is occurring.xe2x80x9d For instance, refer to Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Edition, Volume 15, pages 494-517, Microwave Technology.
Related United States microwave patents include.
Referring to the above list, Cha ""663 discloses the enhancement of wet oxidation by microwaves utilizing carbonaceous material. Wet oxidation involves a water medium saturated with oxygen and containing organic contaminants, such as hazardous solvents, but not containing biological material. The process shows that such carbonaceous material, often activated carbon, preferentially absorbs microwaves in the presence of water.
Cha et al. disclose the enhancement of gaseous decomposition from a solution by microwaves utilizing carbonaceous material. An important example is the wet calcination of bicarbonate solutions, such as trona. The decomposition reaction is restricted to inorganic chemicals. The process shows that such carbonaceous material, often activated carbon, preferentially absorbs microwaves in the presence of water.
Cha ""988 discloses the decomposition of hazardous materials by the use of microwaves enhanced by carbonaceous material, often activated carbon. The hazardous material is restricted to those organic compounds that are legally classified in this manner and not to material that could be classified as only harmful. A selected microorganism, pseudomonas bacteria, which is not a biological agent, was also decomposed. The process shows that the required decomposition occurs either with a water or gaseous medium.
Cha ""023 discloses the purification of air by microwaves along with carbonaceous material, often activated carbon. The bed of carbonaceous material adsorbs the air contaminants, such as volatile organic compounds, and leaves purified air. Then microwaves along with a purge gas regenerate the carbonaceous material, and the purge gas then passes to an oxidation catalyst bed for further microwave-enhanced oxidation of the purge gas contaminants. The actual air purification is a conventional activated carbon bed process while microwaves are only employed to regenerate the bed and further enhance oxidation of the purge gas. The air contaminants are commonly organic compounds such as hazardous solvents. The process showed an efficient procedure to purify large amounts of air such as is found with clean room applications, and in particular showed that the oxidation catalyst bed enhanced by microwaves and carbonaceous material is very efficient in handling the destruction of hazardous gas-borne materials.
The objectives of the present invention include overcoming the above-mentioned deficiencies in the prior art and providing a potentially economically viable process for the microwave destruction of contaminated waste, consisting essentially of chemical and biological agents and harmful medical waste, by employing carbonaceous materials to enhance the efficiency of the microwaves while keeping the bulk temperature down to only a modest rise.